Multivitamins are a household staple. In fact , 74% of adults in the US take some form of dietary supplement, according to the Council for Responsible Nutrition.

But Dr. Thao Tran, a primary care physician, warns against relying on them.

“If you’re taking it for the hope that it will treat something or provide mortality benefits or provide some sort of longevity,” Dr. Tran says, “that has been shown to not be the case from a lot of our studies.”

For the average person

Studies have shown multivitamin supplements are not necessarily beneficial to the average person. Those eating a balanced diet likely don’t need the extra vitamins and minerals.

While multivitamins aren’t necessarily bad for you, taking an excess of something your body doesn’t need may be a waste at best and, at worst, actually harmful.

Water-soluble vitamins are processed through the kidneys. “And if you take in excess,” Dr. Tran says, “your body will naturally eliminate those through your urine.”

Fat-soluble vitamins, which include vitamins A, D, E, and K, are stored in the liver. And according to Dr. Tran, “it can actually accumulate to toxic levels.”

When they help

Multivitamins are not without purpose, though. Dr. Tran says they may be beneficial for certain populations.

Some conditions, such as celiac disease or short gut syndrome, may make absorbing nutrients from food more difficult. Patients who have had gastric bypass surgeries or take certain medications may also deal with poor absorption. Multivitamins can help compensate for the nutrients lost.

Those who follow vegetarian, vegan, or other restricted diets may not get adequate amounts of certain vitamins or minerals from their food. Anyone living in areas with limited access to nutritious food may find multivitamins help meet their nutritional needs.

All vitamins aren’t created equal

If you decide to take multivitamins, it will require more thought than throwing a bottle in your cart. For one, the kind of vitamin matters.

“If you look at the nutrition label,” Dr. Tran says, “you will see that the pill multivitamins often contain significant amounts more vitamin than the chewable.”

Often, gummy vitamins can’t contain some vitamins and minerals found in the pill form. Things like calcium and iron may be missing.

So, while the term “multivitamin” may suggest you’re filling the nutrition gaps in your diet, Dr. Tran says “All that means is that there are more than two vitamins in it.”

Focus on a healthy diet

Taking a multivitamin may be easier than sourcing, preparing, and eating a healthy, balanced diet. But the idea that they make up for unhealthy eating is too good to be true.

“If you were going to fully invest in the best health,” Dr. Tran says, “it needs to come from the diet. Nothing can replace that.”

Those who can’t enjoy the full benefits of a healthy diet can get the extra nutrients they need, but the pills aren’t supposed to replace a balanced plate.

“The supplement is—that’s it—just a supplement to a healthy diet.”